Ester base lubricants



United States Patent 3,344,068 ESTER BASE LUBRICANTS Francis H. Waight, Mold, and Alexander C. B. MacPhail, Wirral, England, assignors to Shell Oil Company, New York, N.Y., a corporation of Delaware No Drawing. Filed May 19, 1965, Ser. No. 457,222 Claims priority, application Great Britain, Mar. 11, 1964, 10,263/64 7 Claims. (Cl. 252-475) This application is a continuation-in-part of application Ser. No. 436,945, filed Mar. 3, 1965 (now abandoned).

This invention relates to an ester base lubricant having good oxidation stability which is particularly useful for lubricating gas turbine engines.

Oils of the invention comprise major amounts of an ester base oil and minor amounts suflicient to enhance the oxidation stability of (1) An N-substituted phenothiazine having the formula R R4 1 R1 7 I) wherein R is selected from a hydrocarbyl group having 1 to 12 carbons, perferably l to 6 carbons, and a cyanoalkyl group having 1 to 20 carbons, preferably 2 to 8 carbons; R is selected from the group consisting of alkyl and alkoxy groups having from 1 to 12, preferably 4 to 8, carbons; and R R and R are selected from the group consisting of hydrogen and C -C preferably C to C alkyl and alkoxy groups; and

(2) A secondary aromatic amine having two aromatic groups attached to the nitrogen atom.

The hydrocarbyl group can be alkyl, aryl, alkaryl, or aralkyl.

The N-substituted phenothiazines of the present invention preferably have one alkyl or alkoxy'radical as substituent in each aromatic ring comprising the phenothiazine molecule and 3,7-substitution is most preferred. Preparation of N-substituted phenothiazines is described, for example, in British Patent No. 873,066, issued July 19, 1961, to Shimmin and Mofiatt. N-substituted phenothiazines which are particularly useful for the purposes of the present invention are -methyl-3,7-dioctyl phenothiazine, lO-n-butyl-3,7-dioctyl phenothiazine, 10-n-octyl- 3,7-dioctyl phenothiazine, l0-phenyl-3,7-dioctyl phenothiazine, 10-tolyl-3,7-dioctyl phenothiazine, lO-cyanoethyl 3,7 dioctyl phenothiazine, lO-cyanopropy1-3,7- dioctyl phenothiazine, 10-cyanobutyl-3,7-dioctyl phenothiazine, l0-benzyl-3,7-dioctyl phenothiazine, IO-benzyl- 3,7 dibutyl phenothiazine, l0 benzyl-3,7-diisopropoxy mixtures thereof.

Any secondary aromatic amine may be used in conjunction with the N-substituted phenothiazines for the purposes of the present invention; certain diphenylamines and N-aryl naphthylamines are, however, preferred. Suitable diphenylamines are unsubstituted diphenylamineand 'those having an alkyl or alkoxy radical containing from to 20 carbon atoms, include phenyl-ot-naphthylamine, phenyl-B-naphthylamine and 13,,3-dinaphthylamine; phenyl phenothiazine, lO-benzyl-Bfl-dibutoxy phenothiazine and 3,344,068 Patented Sept. 26, 1967 ice a-naphthylamine is preferred. It also appears that when the ester comprising the major proportion of the present ester base composition is a simple ester it is preferable to use diphenylamines, e.g., p,p'-dioctyldiphenylamine, especially in admixture with N-aryl naphthylamines, as the secondary aromatic amine, Whereas N-aryl naphthylamines, e.g. phenyl-a-naphthylamine, appear to be preferable for use with ployesters.

The additives of the invention are employed in minor amounts sufiicient to enhance the oxidation stability of the oil; in general, they will be present in an amount of 0.05 to 10% by weight, preferably 0.1 to 5% by weight of the final composition.

Esters suitable as the ester base in the composition of the present invention are simple esters, complex esters, polyesters, or mixtures thereof to which may be added other additives, depending upon the properties desired for the composition and the temperature conditions under which it is to be used. By simple ester is meant an ester formed between an aliphatic dicarboxylic acid and an aliphatic monohydric alcohol, preferred simple esters being formed from an aliphatic dicarboxylic acid containing from 6 to .10 carbon atoms in the molecule and a branched chain monohydric alcohol containing from 6 to 12 carbon atoms in the molecule, especially those alcohols having no hydrogen on the beta carbon atom. Examples of simple esters useful for the purposes of the present invention are diisooctyl sebacate, di(2-ethyl hexyl) sebacate, diisooctyl azelate, di(3,5,5-t-rimethyl hexyl) adipate, Z-ethyl hexyl-3,5,5-trimethyl hexyl sebacate and 2,2,4-trimethyl pentyl azelate.

By complex ester is meant an ester formed from various combinations of an aliphatic dicarboxylic acid, a glycol or polyglycol and either or both of an aliphaticmonohydric alcohol 'and an aliphatic monocarboxylic acid. Some typical complex ester structures are represented by AD (GD)nA, A(DG)nM and MG(DG)nM, wherein A, D, G and M represent the esterification residues from an aliphatic monohydric alcohol, an aliphatic dicarboxylic acid, a glycol or polyglycol and an aliphatic monocarboxylic acid respectively and n is a number from 1 to ethyl hexyl alcohol, caproic acids, pelargonic acid, capric acid, neopentyl glycol, ethylene glycol, propylene glycol, polyglycols such as polyethylene glycols, sebacic acid, adipic acid, azelaic acid and pimelic acid.

By polyesters in meant esters made from aliphatic alcohols having therein at least 3 hydroxyl groups, for example esters made from trimethylol propane. Tetraesters such as pentaerythritol tetraesters of dimers or trimers of the same and dipentaerythritol esters of C -C acids, especially C C acids, are particularly preferred. These esters are commerically available from Hercules Chemical Company.

Thickeners may also be added to oils of the invention to improve viscosity properties. Suitable thickeners are polymers of esters of acrylic or an alkyl substituted acrylic acid, for example lauryl methacrylate, or an ether of a polyoxyalkylene glycol of the general formula R O(R O),,R wherein R is an alkyl group, R is hydrogen or an alkyl group, R is an alkylene group of 2 to 4 carbon atoms and n is a number greater than unity. Suitable compounds are marketed under the trade name Uncon, specific examples being b13385, b13525, LB625. Alsosuitable are copolymers of propylene oxide and ethylene oxide marketed under the trade name Gxilube, e.g. Oxilube /140. The thickeners may be used in proportions of up to 40% by weight calculated on the final lubricant composition depending upon the viscomet-ric properties'required for said lubricant.

The ester base compositions of the present invention may additionally contain extreme pressure additives, additional antioxidants, metal deactivators, anti-corrosion agents, anti-foaming agents, dyestuffs, and other additives chloromethylphosphonic acid salts of C1842 tertiary alkyl primary amines.

A wide variety of materials may be used as metal deactivators and anti-corrosion agents, depending on the known to be suitable for use with ester base lubricant 5 metal or metals with which the ester base composition formulations. of the present invention will come into contact. Materials Suitable E.P. agents are esters of acids of phosphorus, which are particularly useful as affording protection of, such as triphenyl phosphorothionate, tritolyl phosphoro for example, copper, copper alloys and silver against corthionate, and trixylyl phosphorothionate; phosphate esrosive attack are the triazoles, for example, 1,2,3-benzters e.g. triphenyl phosphate and tritolyl phosphate may triazole, methyl-1,2,3-benztriazole, 3-amino-5-methyl-1, also be used but are preferably used in conjunction with 2,4-triazole, especially 3-amino-5-phenyl-1,2,4-triazole, a minor proportion e.g. 0.1% weight based on the whole 3-amino-5-pyridyl-1,2,4-triazole, 3-an1ino-5-anilido-1,2,4- lubricant formulation of a secondary amine such as ditriazole and .5,5'-diamino-3,3-bi(1,2,4-triazole), used in methyl (3,5-ditertiary butyl-4-hydroxy benzyl)amine. amounts up to about 1%, preferably about 0.5% wt. of Another class of phosphorus-containing E.P. additives the composition. Also useful for providing protection for which may be employed in ester base compositions of metals such as copper, cadmium, silver and magnesium the present invention are diaryl haloalkyl phosphates, are minor amounts, e.g. up to 1% by weight, preferably e.g. diphenyl-2,2-bis(chloromethyl)3-chloromethyl phosup to 0.5% by weight of pyridylamines, particularly diphorothionate. Yet another class of BF. additives which pyridylarnines, e.g. 2,2'-dipyridylamine. Small propormay usefully be employed in the present 'ester base comtions, e.g. from 0.01 to 0.2% by weight, of se'bacic, azelaic positions are the chlorinated dior polyphenyls, i.e. dior adipic acid are useful as inhibitors of lead corrosion phenyls, terphenyls, higher polyphenyls or mixtures therewhile metal petroleum sulfonates, e.g. calcium petroleum of containing at least one chlorine atom attached directsulfonate, are useful as rust inhibitors. ly to each benzene nucleus, for example chlorinated di Suitable antirfoaming agents are the polydimethyl siloxor polyphenyls sold under the trade name Arochlor. anes having viscosities from 100 to 100,000 centistokes Still another class of E.P. additives suitable for use in at 25 C. ester base compositions of the present invention are sub- To illustrate the ester base compositions of the present stituted oxetane polymers, i.e. polymers prepared from invention, compositions as shown in Table I (Examples oxetanes having the formula I-III and VII-VIII) were formulated and thereafter compared with corresponding compositions (Examples IV- XaC 0H, VI and IX-X) not in accordance with the present invention by means of one or more of three test procedures, viz. the oxidation/corrosion test at 175 C. set forth in X30 CH: US. Military Specification MIL-L 7808D, a low-temperature storage test and an accelerated storage test. In the h i one X i hl i or b i d h others storage tests samples of compositions in accordance with are chosen from hydrogen, chlorine or bromine, e.g. 3,3- the Pmsent invention and Comparative eXamPIBS not in bis(chloromethyl)oxetane. accordance with the present invention were stored in con- A class of BF. additives which are particularly useful miners having loosely fitting lids, maintained at p for imparting extra resistance to extreme pressure contures 01 'afld and examined PeFiOdiCaHY ditions are the monochloromethylphosphonic acid salts after periods up to three months for the presence of susof tertiary alkyl primary amines, for example the monopended matter.

TABLE I Composition of Examples I-X I II III IV V VI VII VIII IX X Di(2-ethyl hexyDsebacate, percent wt. Dllsooctyl azelate, percent wt Diisodecyl azelate, percent wt 2,2,4-trlmethyl pentyl azelate, percent wt. Trlmethylol propane tripelargonate, percent wt Hercolube A, percent wt Oxilube 1 /140, percent wt 10-benzyl-3,7-di0ctyl phenothiazine, percent wt. 3,7-dioctyl phenothlazine, percent wt Phenyl-a-nnphthylamine, percent wt...

Aroclor 3 1254, percent wt "Irlphenyl phosphorothionate, percent Wt. s-methyl benzotriazole, p.p.m 3-an1ino-5-anilido-l,2,4-trlazole p p Azelaic acid, percent wt. Silicone MS 200 12500, p.p. Polymer of 3,3 -bis(chlorom l) (m 450, Cl content 45%), percent wt l C C"; acid esters of pentaerythritol. 1 Copolymers of ethylene oxide and propylene oxide. Chlorinated diphenyl.

TABLE II Volatility Acidity Viscosity Metal Weight Change, mgJcru. Example No. Loss, Increase, Increase, Percent mg. KOH/g. Percent wt Cu Mg Ag A1 Fe 0. 8 1. 25 12. 0 Nil Nil Nil Nil Nil 0. 6 1. 5 12. 2 -0. 10 Nil 0. 12 Nil 0. 02 0. 4 0. 6 2. 6 0. 03 Nil +0. 02 Nil Nil 0. 7 1. 20 11. 8 0. 04 Nil Nil Nil -0. 02 1. 2 1. 5 12. 6 Nil +0.12 0. 3 Nil 0. 02 0. 4 0. 4 2. 5 0. 02 +0. 02 Nil Nil Nil Specification Limits 2.0 5 to +15 it). 4 =!=0. 2 i0. 2 5:0. 2 i0. 2

From Table II it is clear that the formulations of Examples I-III (i.e. formulations according to the invention) all show a resistance to oxidation and corrosion at high temperature which is at least as good as that shown by the comparative formulations IV-VI (i.e. formulations outside of the invention) while the formulation of Example I has exceptional high-temperature oxidation and corrosion resistance. Referring now to Table III it is clear that only the formulations of Examples I- III and VIIVIII (i.e. formulations according to the present invention) give satisfactory performance in the storage tests. Four samples of each of the formulations of Examples VII-X were also subjected to low-temperature C.) storage for a period of a year and were examined for suspended matter at intervals of a few weeks. All of the samples of Examples VII and VIII so stored (i.e. samples of compositions of the invention) remained clear and bright throughout the entire low-temperature test period, whereas the behavior of samples of the comparative Examples IX and X was variable, one sample of each example remaining clear, some samples of each example giving deposition in the first few days of storage, while all of the remaining samples gave deposition before the end of the test period.

TABLE III tion with an N-substituted phenothiazine, while Example XII gave less benzene insolubles, a small viscosity increase and a smaller acidity increase than did the composition of Example XIII, which comprised a simple ester and phenyl-a-naphthylamine in conjunction with an N- substituted phenothiazine.

N-cyanoalkyl substituted phenothiazines suitable for the purposes of the present invention are those having up to 20, preferably from 2 to 8, carbon atoms in the alkyl chain of the cyano alkyl radical and preferably have one Condition of Sample after- Example No. 15 C. 80 C.

3 months 3 weeks 5 weeks 7 weeks 8 weeks I 12 weeks White ppt. Cloudy Clear Clear- -do do Do.

O1oudy- Deposition. Medium deposition. Deposition. Medium deposition Heavy deposition.

To illustrate the advantage to be gained from employing a diphenylamine, particularly when admixedwith an N-aryl naphthylamine, in conjunction with the N-substituted phenothiazine, when the ester comprising the major proportion of the ester base composition of the present invention is a simple ester, the compositions referred to as Examples XI, XII and XIII in Table IV were tested by. means of the Rolls Royce Blown Oxidation Test. In this test, 250 ml. per minute of air or nitrogen, saturated with water vapor, are bubbled under controlled conditions through a 50-ml. sample of the ester base composition under test at a temperature of 198 C. for a period of 192 hours. Deterioration of the composition due to oxidation is then measured in terms of acidity, viscosity change and benzene insolubles.

TABLE IV Example/Composition, percent wt. XI XII XIII Diisooctylazelate 94. 0 93. 5 96. 0 10-benzyl-3,7-di0cty1 phenothiazine 0. 5 0. 5 0. 5 Phenyl-wnaphthylami no 0. 5 0. 5 p,p-Dioctyldiphenylamine 2. O 2. 0 Azelaie acid 0. 02 0. 02 0. 02 Aroolor 1254 3. 0 3. 0 3. 0 3 arnino 5-anilido 1,2,4-triazole (p 25 25 Silicone MS ZOO/12500 (p.p.m.) 5 5 5 The results obtained are appended at Table V, from which it is seen that the composition of Example XI, which comprised a simple ester and a mixture of secondary aromatic amines in conjunction with an N-substituted phenothiazine, gave less benzene insolubles, a smaller viscosity increase and a smaller acidity increase than did the composition of Example XII, which comprised a simple ester and a diphenylamine in conjunc- TABLE VII Example/ Composition, percent wt.

Diisooctylazelate 10-eyanoethyl3,7-dioctyl phenothiazine.. 10-benzyl-3,7-dioctyl phenothiazine p,p-Dioctyldiphenylamine Triphenylphosphorothionate.

Arochlor 1254 a chlorinated diphenyl) Azelaic acid 3-amino-5-phenyl-1,2,4-triazole (p.p.m.) Silicone MS 200/12500 (p.p.m.)

The results obtained are set out at Table VIII from which it is seen that the composition of Example XV which comprises an N-cyanoalkyl substituted phenothiazine and a secondary aromatic amine gives a performance in the Rolls Royce Blown Oxidation Test which is at least as good as that given by the composition of Example XVI (a composition of the present invention) comprising 10-benzyl-3,7-dioctyl phenothiazine.

TABLE VIII Benzene Viscosity at 210 Increase in Acid Example No. Insolubles, F., 05., percent Value, mg.

percent wt. increase KOH/g.

X 0. 02 9. 4. 3 XVI 0.01 9. 5 6.3

The results obtained by submitting further compositions in accordance with the present invention to the Rolls Royce Blown Oxidation Test are set out at Table IX and are identified as Examples XVII to XXI. In these examples the formulation of Example XV was used except that the substituent on the nitrogen atom of the substituted phenothiazi-ne was varied.

TABLE IX substituent Benzene Viscosity at Increase in Example on Nitrogen Insolubles, 210 F., cs., Acid Value, N 0. Atom percent wt. percent mg. KOH/g.

increase 0.03 8 4. 9 0.03 8 3. 8 0. 01 7 Nil 0. 01 7 Nil 0.01 7. 5 0. 02

A further example still (Example XXII) of a composition in accordance with the present invention is given at Table X.

Component TABLE X Percent wt.

MS 200/ 12,500, 5 p.p.m.

When subjected to the Rolls Royce Blown Oxidation Test carried out at a test temperature of 225 C., the formulation of Example XXII (Table X) gave only 0.01% weight benzene insolubles and an increase in acidity of 4.9 mg. KOH/ g. Furthermore the composition gave no deposition after storage for twelve weeks at a tem- Z8 perature of C. and has highly desirable load-carrying properties, giving an I.A.E.. gear rig scufiing load of 66 lbs. lever load under condition C of LP. Method No. 166 and a Ryder gear rig scufling load in excess of 3,300 lbs.

We claim as our invention:

1. A lubricating composition comprising a major amount of an ester base lubricating oil and minor amounts sufiicient to increase the oxidation stability of the oil of (1) 10-benzyl-3,7-dioctylphenothiazine, and

(2) a secondary aromatic amine having two aromatic groups attached to the nitrogen atom.

2. The composition of claim 1 wherein the secondary aromatic amine is a diphenylamine.

3. The composition of claim 1 wherein the secondary aromatic amine is a p,p-disubstituted diphenylamine.

4. The composition of claim 1 wherein the secondary aromatic amine is a N-aryl naphthylamine.

5. The composition of claim 1 wherein the secondary aromatic amine is phenyl-a-naphthylamine.

6. A lubricating composition comprising a major amount of an ester base lubricating oil and about 0.1 to about 5% by weight of each of 10-benzyl-3,7-dioctylphenothiazine and phenyl-u-naphthylamine.

7. A lubricating composition comprising a major amount of an ester base lubricating oil and about 0.1 to about 5% by weight of each of l0-benzyl-3,7-dioctylphenothiazine and p,p'-dioctyl diphenylamine.

References Cited UNITED STATES PATENTS 2,587,661 3/1952 Smith 2527 2,930,758 3/1960 Tierney et a1. 252403 2,971,912 2/1961 Elliott et a1. 25247.5 3,014,888 12/1961 Shimmin et a1. 25247 3,218,256 11/1965 Edwards et a1. 25247.5

FOREIGN PATENTS 1,296,477 5/ 1962 France.

824,521 12/ 1959 Great Britain. 933,505 8/1963 Great Britain.

OTHER REFERENCES Murphy et al.: Mode of Action of Phenothiazine Type Antioxidants, Industrial & Engineering Chemistry, December 1950, pages 2479-2489.

DANIEL E. WYMAN, Primary Examiner.

L. G. XIARHOS, W. H. CANNON, Assistant Examiners. 

1. A LUBRICATING COMPOSITION COMPRISING A MAJOR AMOUNT OF AN ESTER BASE LUBRICATING OIL AND MINOR AMOUNTS SUFFICIENT TO INCREASE THE OXIDATION STABILITY OF THE OIL OF (1) 10-BENZYL-3,7-DIOCTYLPHENOTHIAZINE, AND (2) A SECONDARY AROMATIC AMINE HAVING TWO AROMATIC GROUPS ATTACHED TO THE NITROGEN ATOM. 